If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You may have to register
before you can post: click the register link above to proceed. To start viewing messages,
select the forum that you want to visit from the selection below.

Are You Confused about LCD and LED?

Maybe I should subtitle this thread, LED is not a new kind of TV.

Now is a popular time to buy a new display. Black Friday, Cyber Monday, Christmas and the end of the year make this an opportune time to buy. There are many choices and it can be confusing. Hopefully this thread will help clear up some of the confusing terms associated with LCD and LED high definition displays. Most of the confusion is associated with the way that LCD displays are backlit.

First off there are two main types of LCD displays, those with traditional CCFL backligting and those that utilize LEDs for backlighting. The propose of the backlight is to project light through the colored pixels, in order to create the image we see. Without the back light, there would be no image on the screen. To make sense of this, take a look at the diagram below.

Back lighting in the first LCD displays used fluorescent backlights, known as CCFL, or Cold Cathode Fluorescent Lamps. (see top photo) CCFL backlighting works great and is fairly inexpensive to build. The disadvantage to this type of backlighting is that the displays have to be deeper to house the CCFL array. Also, you have less dimming options. The backlight can only dim so low before you have problems with flickering and you have to dim or brighten the entire array as a whole.

](edge lit LED backlighting)

Using a LED light source allows the backlight to be dimmed to a lower level, thus increasing contrast. LEDs also use less energy and allow manufacturers to build thinner displays since the LEDs take up less depth. Sounds great huh? Well it is but it also creates more terms to get straight.

Edge Lighting v/s Full Array Backlighting....and then there is Local Dimming
Edge lighting is the lest expensive LED option. With edge lighting the LEDs are placed around the edge of the screen and can illuminate all the pixels across the screen. On smaller screens, 42 inches and less, this works out fairly well. On larger screens, edge lighting can create brighter lighting around the edges when compared to the middle. This type of uniformity problem can be very distracting.

(full array LED backlighting)

Full array backlighting, as the name suggests, places LEDs behind the entire surface of the screen. This provides even lighting of the screen, thus eliminating any "hot spots". As you can imagine, full array backlighting is more expensive but it is the preferred method of backlighting especially on larger screens.

Local dimming takes back lighting to a whole new level of control as it creates individual zones of LEDs, can be dimmed or brightened independently. This "zone dimming" can greatly increase the black levels and contrast of the image If it weren't confusing enough, local dimming can be found on both edge lit and full array lit models, although full array with local dimming is the most desired and best performing LED backlighting technology.

As a whole, LED displays are brighter than tradition LCD. People who have a lot of ambient light in their viewing room may benefit from the additional brightness. LCDs have long suffered a lack of contrast when compared to Plasma displays. However, LED with full array backlighting and local dimming has come close to leveling the contrast playing field. When compared to Plasma, they are more energy efficient, thinner and weigh less. However, off-angle viewing and picture uniformity remain a sticking point.

Posting Permissions

Please support HomeTheaterEquipment.com by purchasing your AV gear (or any other stuff) via Amazon.com. We get a few bucks here and there, which helps us create more and more top-level reviews and content for you to enjoy on all of our sites!